I need a wiring diagram or service manual for the soundsticks II

I found this useful pinout on Nick Brook’s site:

https://nickbrook.me/blog/2014-08-11/rep...

The R speakers are driven between pins 1 and 2 of the s-video 4 pin connector (the two furthest-apart ones, at the bottom, white and translucent in the cable). Pins 3 and 4 connect to the touch-sensitive pads on the R speaker for volume down (3) and volume up (4); you should be able to control the speaker volume by simply touching a bare wire connected to these pins with your finger (I think it detects mains hum or something). Note: Touching both volume controls at once puts the system into “mute” mode, which can make the system appear not to work. Simply touch volume up again to unmute.

As you have found, the L speaker is simply driven between the two connectors of the RCA plug.

The original satellite speakers consist of four 8 ohm drivers in parallel, so the amp is expecting a 2 ohm load.